Java tutorial
package net.yck.wkrdb.common.shared; /* * Licensed to the Apache Software Foundation (ASF) under one or more * contributor license agreements. See the NOTICE file distributed with * this work for additional information regarding copyright ownership. * The ASF licenses this file to You under the Apache License, Version 2.0 * (the "License"); you may not use this file except in compliance with * the License. You may obtain a copy of the License at * * http://www.apache.org/licenses/LICENSE-2.0 * * Unless required by applicable law or agreed to in writing, software * distributed under the License is distributed on an "AS IS" BASIS, * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. * See the License for the specific language governing permissions and * limitations under the License. */ import java.awt.Color; import java.lang.reflect.Constructor; import java.lang.reflect.InvocationTargetException; import java.math.BigDecimal; import java.math.BigInteger; import java.net.InetAddress; import java.net.MalformedURLException; import java.net.URL; import java.net.UnknownHostException; import java.text.ParseException; import java.text.SimpleDateFormat; import java.util.Calendar; import java.util.Date; import java.util.Locale; import org.apache.commons.configuration2.convert.DefaultConversionHandler; import org.apache.commons.configuration2.ex.ConversionException; import org.apache.commons.lang3.BooleanUtils; import org.apache.commons.lang3.StringUtils; /** * A utility class to convert the configuration properties into any type. * * @author Emmanuel Bourg * @version $Id: PropertyConverter.java 1672933 2015-04-11 20:36:41Z oheger $ * @since 1.1 */ final class PropertyConverter { /** Constant for the prefix of hex numbers. */ private static final String HEX_PREFIX = "0x"; /** Constant for the radix of hex numbers. */ private static final int HEX_RADIX = 16; /** Constant for the prefix of binary numbers. */ private static final String BIN_PREFIX = "0b"; /** Constant for the radix of binary numbers. */ private static final int BIN_RADIX = 2; /** * Constant for the argument classes of the Number constructor that takes a * String. */ private static final Class<?>[] CONSTR_ARGS = { String.class }; /** * The fully qualified name of {@code javax.mail.internet.InternetAddress} */ private static final String INTERNET_ADDRESS_CLASSNAME = "javax.mail.internet.InternetAddress"; /** * Private constructor prevents instances from being created. */ private PropertyConverter() { // to prevent instantiation... } /** * Performs a data type conversion from the specified value object to the * given target data class. If additional information is required for this * conversion, it is obtained from {@code DefaultConversionHandler.INSTANCE} * object. If the class is a primitive type (Integer.TYPE, Boolean.TYPE, * etc), the value returned will use the wrapper type (Integer.class, * Boolean.class, etc). * * @param cls * the target class of the converted value * @param value * the value to convert * @return the converted value * @throws ConversionException * if the value is not compatible with the requested type */ public static Object to(Class<?> cls, Object value) throws ConversionException { if (cls.isInstance(value)) { return value; // no conversion needed } if (String.class.equals(cls)) { return String.valueOf(value); } if (Boolean.class.equals(cls) || Boolean.TYPE.equals(cls)) { return toBoolean(value); } else if (Character.class.equals(cls) || Character.TYPE.equals(cls)) { return toCharacter(value); } else if (Number.class.isAssignableFrom(cls) || cls.isPrimitive()) { if (Integer.class.equals(cls) || Integer.TYPE.equals(cls)) { return toInteger(value); } else if (Long.class.equals(cls) || Long.TYPE.equals(cls)) { return toLong(value); } else if (Byte.class.equals(cls) || Byte.TYPE.equals(cls)) { return toByte(value); } else if (Short.class.equals(cls) || Short.TYPE.equals(cls)) { return toShort(value); } else if (Float.class.equals(cls) || Float.TYPE.equals(cls)) { return toFloat(value); } else if (Double.class.equals(cls) || Double.TYPE.equals(cls)) { return toDouble(value); } else if (BigInteger.class.equals(cls)) { return toBigInteger(value); } else if (BigDecimal.class.equals(cls)) { return toBigDecimal(value); } } else if (Date.class.equals(cls)) { return toDate(value, DefaultConversionHandler.INSTANCE.getDateFormat()); } else if (Calendar.class.equals(cls)) { return toCalendar(value, DefaultConversionHandler.INSTANCE.getDateFormat()); } else if (URL.class.equals(cls)) { return toURL(value); } else if (Locale.class.equals(cls)) { return toLocale(value); } else if (isEnum(cls)) { return convertToEnum(cls, value); } else if (Color.class.equals(cls)) { return toColor(value); } else if (cls.getName().equals(INTERNET_ADDRESS_CLASSNAME)) { return toInternetAddress(value); } else if (InetAddress.class.isAssignableFrom(cls)) { return toInetAddress(value); } throw new ConversionException("The value '" + value + "' (" + value.getClass() + ")" + " can't be converted to a " + cls.getName() + " object"); } /** * Convert the specified object into a Boolean. Internally the * {@code org.apache.commons.lang.BooleanUtils} class from the * <a href="http://commons.apache.org/lang/">Commons Lang</a> project is * used to perform this conversion. This class accepts some more tokens for * the boolean value of <b>true</b>, e.g. {@code yes} and {@code on}. Please * refer to the documentation of this class for more details. * * @param value * the value to convert * @return the converted value * @throws ConversionException * thrown if the value cannot be converted to a boolean */ public static Boolean toBoolean(Object value) throws ConversionException { if (value instanceof Boolean) { return (Boolean) value; } else if (value instanceof String) { Boolean b = BooleanUtils.toBooleanObject((String) value); if (b == null) { throw new ConversionException("The value " + value + " can't be converted to a Boolean object"); } return b; } else { throw new ConversionException("The value " + value + " can't be converted to a Boolean object"); } } /** * Converts the specified value object to a {@code Character}. This method * converts the passed in object to a string. If the string has exactly one * character, this character is returned as result. Otherwise, conversion * fails. * * @param value * the value to be converted * @return the resulting {@code Character} object * @throws ConversionException * if the conversion is not possible */ public static Character toCharacter(Object value) throws ConversionException { String strValue = String.valueOf(value); if (strValue.length() == 1) { return Character.valueOf(strValue.charAt(0)); } else { throw new ConversionException( String.format("The value '%s' cannot be converted to a Character object!", strValue)); } } /** * Convert the specified object into a Byte. * * @param value * the value to convert * @return the converted value * @throws ConversionException * thrown if the value cannot be converted to a byte */ public static Byte toByte(Object value) throws ConversionException { Number n = toNumber(value, Byte.class); if (n instanceof Byte) { return (Byte) n; } else { return n.byteValue(); } } /** * Convert the specified object into a Short. * * @param value * the value to convert * @return the converted value * @throws ConversionException * thrown if the value cannot be converted to a short */ public static Short toShort(Object value) throws ConversionException { Number n = toNumber(value, Short.class); if (n instanceof Short) { return (Short) n; } else { return n.shortValue(); } } /** * Convert the specified object into an Integer. * * @param value * the value to convert * @return the converted value * @throws ConversionException * thrown if the value cannot be converted to an integer */ public static Integer toInteger(Object value) throws ConversionException { Number n = toNumber(value, Integer.class); if (n instanceof Integer) { return (Integer) n; } else { return n.intValue(); } } /** * Convert the specified object into a Long. * * @param value * the value to convert * @return the converted value * @throws ConversionException * thrown if the value cannot be converted to a Long */ public static Long toLong(Object value) throws ConversionException { Number n = toNumber(value, Long.class); if (n instanceof Long) { return (Long) n; } else { return n.longValue(); } } /** * Convert the specified object into a Float. * * @param value * the value to convert * @return the converted value * @throws ConversionException * thrown if the value cannot be converted to a Float */ public static Float toFloat(Object value) throws ConversionException { Number n = toNumber(value, Float.class); if (n instanceof Float) { return (Float) n; } else { return new Float(n.floatValue()); } } /** * Convert the specified object into a Double. * * @param value * the value to convert * @return the converted value * @throws ConversionException * thrown if the value cannot be converted to a Double */ public static Double toDouble(Object value) throws ConversionException { Number n = toNumber(value, Double.class); if (n instanceof Double) { return (Double) n; } else { return new Double(n.doubleValue()); } } /** * Convert the specified object into a BigInteger. * * @param value * the value to convert * @return the converted value * @throws ConversionException * thrown if the value cannot be converted to a BigInteger */ public static BigInteger toBigInteger(Object value) throws ConversionException { Number n = toNumber(value, BigInteger.class); if (n instanceof BigInteger) { return (BigInteger) n; } else { return BigInteger.valueOf(n.longValue()); } } /** * Convert the specified object into a BigDecimal. * * @param value * the value to convert * @return the converted value * @throws ConversionException * thrown if the value cannot be converted to a BigDecimal */ public static BigDecimal toBigDecimal(Object value) throws ConversionException { Number n = toNumber(value, BigDecimal.class); if (n instanceof BigDecimal) { return (BigDecimal) n; } else { return new BigDecimal(n.doubleValue()); } } /** * Tries to convert the specified object into a number object. This method * is used by the conversion methods for number types. Note that the return * value is not in always of the specified target class, but only if a new * object has to be created. * * @param value * the value to be converted (must not be <b>null</b>) * @param targetClass * the target class of the conversion (must be derived from * {@code java.lang.Number}) * @return the converted number * @throws ConversionException * if the object cannot be converted */ static Number toNumber(Object value, Class<?> targetClass) throws ConversionException { if (value instanceof Number) { return (Number) value; } else { String str = value.toString(); if (str.startsWith(HEX_PREFIX)) { try { return new BigInteger(str.substring(HEX_PREFIX.length()), HEX_RADIX); } catch (NumberFormatException nex) { throw new ConversionException( "Could not convert " + str + " to " + targetClass.getName() + "! Invalid hex number.", nex); } } if (str.startsWith(BIN_PREFIX)) { try { return new BigInteger(str.substring(BIN_PREFIX.length()), BIN_RADIX); } catch (NumberFormatException nex) { throw new ConversionException("Could not convert " + str + " to " + targetClass.getName() + "! Invalid binary number.", nex); } } try { Constructor<?> constr = targetClass.getConstructor(CONSTR_ARGS); return (Number) constr.newInstance(str); } catch (InvocationTargetException itex) { throw new ConversionException("Could not convert " + str + " to " + targetClass.getName(), itex.getTargetException()); } catch (Exception ex) { // Treat all possible exceptions the same way throw new ConversionException( "Conversion error when trying to convert " + str + " to " + targetClass.getName(), ex); } } } /** * Convert the specified object into an URL. * * @param value * the value to convert * @return the converted value * @throws ConversionException * thrown if the value cannot be converted to an URL */ public static URL toURL(Object value) throws ConversionException { if (value instanceof URL) { return (URL) value; } else if (value instanceof String) { try { return new URL((String) value); } catch (MalformedURLException e) { throw new ConversionException("The value " + value + " can't be converted to an URL", e); } } else { throw new ConversionException("The value " + value + " can't be converted to an URL"); } } /** * Convert the specified object into a Locale. * * @param value * the value to convert * @return the converted value * @throws ConversionException * thrown if the value cannot be converted to a Locale */ public static Locale toLocale(Object value) throws ConversionException { if (value instanceof Locale) { return (Locale) value; } else if (value instanceof String) { String[] elements = ((String) value).split("_"); int size = elements.length; if (size >= 1 && ((elements[0]).length() == 2 || (elements[0]).length() == 0)) { String language = elements[0]; String country = (size >= 2) ? elements[1] : ""; String variant = (size >= 3) ? elements[2] : ""; return new Locale(language, country, variant); } else { throw new ConversionException("The value " + value + " can't be converted to a Locale"); } } else { throw new ConversionException("The value " + value + " can't be converted to a Locale"); } } /** * Convert the specified object into a Color. If the value is a String, the * format allowed is (#)?[0-9A-F]{6}([0-9A-F]{2})?. Examples: * <ul> * <li>FF0000 (red)</li> * <li>0000FFA0 (semi transparent blue)</li> * <li>#CCCCCC (gray)</li> * <li>#00FF00A0 (semi transparent green)</li> * </ul> * * @param value * the value to convert * @return the converted value * @throws ConversionException * thrown if the value cannot be converted to a Color */ public static Color toColor(Object value) throws ConversionException { if (value instanceof Color) { return (Color) value; } else if (value instanceof String && !StringUtils.isBlank((String) value)) { String color = ((String) value).trim(); int[] components = new int[3]; // check the size of the string int minlength = components.length * 2; if (color.length() < minlength) { throw new ConversionException("The value " + value + " can't be converted to a Color"); } // remove the leading # if (color.startsWith("#")) { color = color.substring(1); } try { // parse the components for (int i = 0; i < components.length; i++) { components[i] = Integer.parseInt(color.substring(2 * i, 2 * i + 2), HEX_RADIX); } // parse the transparency int alpha; if (color.length() >= minlength + 2) { alpha = Integer.parseInt(color.substring(minlength, minlength + 2), HEX_RADIX); } else { alpha = Color.black.getAlpha(); } return new Color(components[0], components[1], components[2], alpha); } catch (Exception e) { throw new ConversionException("The value " + value + " can't be converted to a Color", e); } } else { throw new ConversionException("The value " + value + " can't be converted to a Color"); } } /** * Convert the specified value into an internet address. * * @param value * the value to convert * @return the converted value * @throws ConversionException * thrown if the value cannot be converted to a InetAddress * * @since 1.5 */ static InetAddress toInetAddress(Object value) throws ConversionException { if (value instanceof InetAddress) { return (InetAddress) value; } else if (value instanceof String) { try { return InetAddress.getByName((String) value); } catch (UnknownHostException e) { throw new ConversionException("The value " + value + " can't be converted to a InetAddress", e); } } else { throw new ConversionException("The value " + value + " can't be converted to a InetAddress"); } } /** * Convert the specified value into an email address. * * @param value * the value to convert * @return the converted value * @throws ConversionException * thrown if the value cannot be converted to an email address * * @since 1.5 */ static Object toInternetAddress(Object value) throws ConversionException { if (value.getClass().getName().equals(INTERNET_ADDRESS_CLASSNAME)) { return value; } else if (value instanceof String) { try { Constructor<?> ctor = Class.forName(INTERNET_ADDRESS_CLASSNAME).getConstructor(String.class); return ctor.newInstance(value); } catch (Exception e) { throw new ConversionException("The value " + value + " can't be converted to a InternetAddress", e); } } else { throw new ConversionException("The value " + value + " can't be converted to a InternetAddress"); } } /** * Calls Class.isEnum() on Java 5, returns false on older JRE. */ static boolean isEnum(Class<?> cls) { return cls.isEnum(); } /** * Convert the specified value into a Java 5 enum. * * @param value * the value to convert * @param cls * the type of the enumeration * @return the converted value * @throws ConversionException * thrown if the value cannot be converted to an enumeration * * @since 1.5 */ static <E extends Enum<E>> E toEnum(Object value, Class<E> cls) throws ConversionException { if (value.getClass().equals(cls)) { return cls.cast(value); } else if (value instanceof String) { try { return Enum.valueOf(cls, (String) value); } catch (Exception e) { throw new ConversionException("The value " + value + " can't be converted to a " + cls.getName()); } } else if (value instanceof Number) { try { E[] enumConstants = cls.getEnumConstants(); return enumConstants[((Number) value).intValue()]; } catch (Exception e) { throw new ConversionException("The value " + value + " can't be converted to a " + cls.getName()); } } else { throw new ConversionException("The value " + value + " can't be converted to a " + cls.getName()); } } /** * Convert the specified object into a Date. * * @param value * the value to convert * @param format * the DateFormat pattern to parse String values * @return the converted value * @throws ConversionException * thrown if the value cannot be converted to a Calendar */ public static Date toDate(Object value, String format) throws ConversionException { if (value instanceof Date) { return (Date) value; } else if (value instanceof Calendar) { return ((Calendar) value).getTime(); } else if (value instanceof String) { try { return new SimpleDateFormat(format).parse((String) value); } catch (ParseException e) { throw new ConversionException("The value " + value + " can't be converted to a Date", e); } } else { throw new ConversionException("The value " + value + " can't be converted to a Date"); } } /** * Convert the specified object into a Calendar. * * @param value * the value to convert * @param format * the DateFormat pattern to parse String values * @return the converted value * @throws ConversionException * thrown if the value cannot be converted to a Calendar */ public static Calendar toCalendar(Object value, String format) throws ConversionException { if (value instanceof Calendar) { return (Calendar) value; } else if (value instanceof Date) { Calendar calendar = Calendar.getInstance(); calendar.setTime((Date) value); return calendar; } else if (value instanceof String) { try { Calendar calendar = Calendar.getInstance(); calendar.setTime(new SimpleDateFormat(format).parse((String) value)); return calendar; } catch (ParseException e) { throw new ConversionException("The value " + value + " can't be converted to a Calendar", e); } } else { throw new ConversionException("The value " + value + " can't be converted to a Calendar"); } } /** * Helper method for converting a value to a constant of an enumeration * class. * * @param enumClass * the enumeration class * @param value * the value to be converted * @return the converted value */ // conversion is safe because we know that the class is an Enum class private static Object convertToEnum(Class<?> enumClass, Object value) { return toEnum(value, enumClass.asSubclass(Enum.class)); } }